Sauber's Nico Hulkenberg and incumbent Scuderia driver Felipe Massa are the front runners for the Finn's seat but Boullier is urging all candidates to remain patient.

And the Frenchman has made it clear that, despite the financial difficulties at the team, there isn't a prerequisite that the new man must come laden with sponsorship cash.

"When it comes to drivers we are not simply looking for a short-term replacement for Kimi - we are looking at where we are going to be in the next five years," said Boullier.

"We can afford to be patient, to ask the candidates to wait as we formulate our strategy for the coming years.

"I hope we do not have to take into account commercial considerations when making decisions on drivers because we have worked hard to build our financial strength without having to rely on sponsorship from a driver.

"We want the strongest line-up possible to continue the progress made in recent seasons - that is the priority."

"With Kimi leaving at the end of the year, Romain knows he has the possibility to build the team up more around himself," Boullier added.

"If you look at the last five races, he has done a great job.

"Since Germany everybody has noticed he has clearly 'switched on' and you can see the highs in every race.

(Photo: Getty)

"Whether we've been fighting for the podium or struggling a little bit, Romain has clearly been matching Kimi's performances, which is no small achievement when you consider the world championship-winning calibre of his teammate.

"The Romain of the last two months is the one we all believed he would become, and I hope he keeps improving.

"If he continues in this way, it means he is 'on it' and delivering the results we all know he is capable of, which is very positive for his prospects in 2014."